As a method for increasing a density of an optical disc, one method is to increase a density in a linear-density direction by reducing a channel bit length, i.e., a mark length, and another method is to make a track pitch narrower. However, in the case where the density is increased in the linear-density direction, inter-symbol interference increases. Meanwhile, in the case where the track pitch is made narrower, leakage of information from an adjacent track (adjacent track crosstalk) increases. Methods for reducing the adjacent track crosstalk (hereinafter, simply referred to as “crosstalk” as appropriate) are proposed.
For example, Patent Literature 1 discloses that crosstalk is canceled by supplying reproduction signals of a track to be reproduced and tracks located on both sides thereof to adaptive equalizer units and controlling tap coefficients of the adaptive equalizer unit.